New electric power systems may include multiple-function energy storage elements. For example, in one instance, an energy storage element may be used as a generation source in order to mitigate transients in the system. In another instance, the energy storage element may be used as a backup device to provide power in case main generation sources fail.
Traditional droop control procedures for power systems typically follow a fixed-slope control line. However, in new electric power systems, as the capacity (e.g., the state of charge) of an energy storage element changes, the fixed slope linear droop control will degrade to a point that may cause instability in the electric power system. To avoid this, a centralized control scheme may be employed. This approach, however, increases the complexity and cost of such electric power systems, and the electric power system's reliability may be comprised when the centralized control system fails.